Experiment of Underwater Acoustic Communication with an Orthogonal Signal Division Multiplexing Scheme in a Harbor

Underwater acoustic (UWA) communication is still a challenging area of research, as methods to deal with large intersymbol interference and Doppler spread are needed. We previously evaluated the performance of an orthogonal signal-division multiplexing (OSDM) scheme in a UWA communication system in a test tank and found that OSDM achieved better bit-error-rate (BER) performance than the single-carrier with decision-feedback-equalizer (DFE) method and the orthogonal frequency-division multiplexing (OFDM) method. However, no experiments have yet been conducted in an actual sea environment, which is much more complex than a test tank. In this paper, we report an initial demonstration of OSDM communication in an actual sea environment. The experiment was performed at a harbor for about 85 h by changing the transmission level. We also performed the communication using single-carrier DFE and OFDM, and confirmed that OSDM with a multichannel receiver is attractive to existing schemes; as in the test-tank results, OSDM achieved the best bit-error-rate performance compared to other schemes with practical complexity. We confirmed that OSDM can achieve a highly reliable communication for UWA channels, such as in shallow water.